Synthesis and characterization of bi-oxo capped trinuclear clusters with the general formula [M.sub.3 (.mu..sub.3 -O).sub.2 (O.sub.2 CR).sub.6 L.sub.3 ].sup.n.+-. (M=Mo, W) are well established. See for example Bino, A.; Ardon, M.; Maor, I.; Kaftory, M.; Dori, Z. J Am. Chem. Soc. 1976, 98, 7093; Bino, A.; Cotton, F. A.; Dori, Z. J Am. Chem. Soc. 1978, 100, 5252; Bino, A.; Cotton, F. A.; Dori, Z.; Koch, S.; Kueppers, H.; Millar, M.; Sekutowski, J. Inorg. Chem. 1978, 17, 3245; Birnbaum, A.; Cotton, F. A.; Dori, Z.; Reisner, G. M.; Schwotzer, W.; Shaia, M. Inorg. Chem. 1983, 22, 2723; Cotton, F. A.; Dori, Z.; Marler, D. O.; Schwotzer, W. Inorg. Chem. 1983, 22, 3104; Birnbaum, A.; Cotton, F. A.; Dori, Z.; Kapon, M. Inorg. Chem. 1984, 23, 1617; and Cotton, F. A.; Dori, Z.; Marler, D. O.; Schwotzer, W. Inorg. Chem. 1984, 23, 4033. This type of cluster contains two capping oxygen atoms sitting above and below the M.sub.3 triangular plane. Each metal-metal bond is bridged by two carboxylate groups, leaving the equatorial position, L, at each metal atom occupied by either water, carboxylate or solvent group. These compounds are mainly prepared from refluxing M(CO).sub.6 in carboxylic acid/anhydride mixtures or reducing MO.sub.4.sup.2- under similar reaction conditions. In cases with bulky carboxylate ligands, the assembly of these compounds usually requires high temperature and pressure to yield enough material for characterization. Since the discovery of this class of cluster compounds, most efforts have been directed to the synthesis and characterization of various trinuclear cluster types (see review in Muller, A.; Jostes, R.; Cotton, F. A. Angew. Chem. Int. Ed. Engl. 1980, 19, 875; Cotton, F. A. Polyhedron, 1986, 5, 3; Cotton, F. A.; Shang, M.; Sun, Z. S. Inorg. Chim. Acta. 1993, 212, 95 and references therein). These studies have demonstrated a wide range of M.sub.3 clusters with various bridging and capping ligands (Bino, A.; Cotton, F. A.; Dori, Z.; Kolthammer, B. W. S. J. Am. Chem. Soc. 1981, 103, 5779; Ardon, M.; Bino A.; Cotton, F. A.; Dori, Z.; Kaftory, M.; Kolthammer, B. W. S.; Kapon, M.; Reisner, G. M. Inorg. Chem. 1981, 20, 4083; Cotton, F. A.; Dori, Z.; Kapon, M.; Marler, D. O.; Reisner, G. M.; Schwotzer, W.; Shaia, M. Inorg. Chem. 1985, 24, 4381; Cotton, F. A.; Felthouse, T. R.; Lay, D. G. Inorg. Chem. 1981, 20, 2219; Cotton, F. A.; Shang, M.; Sun, Z. S. J. Am. Chem. Soc. 1991, 13, 3007; and Cotton, F. A.; Shang, M.; Sun, Z. S. J. Cluster Sci. 1992, 3, 123). Relatively little is known about the reactivity of bi-oxo capped clusters, [M.sub.3 (.mu..sub.3 O).sub.2 (O.sub.2 CR).sub.6 L.sub.3 ].sup.n.+-. (M=Mo, W), partly due to their remarkable stability demonstrated by Cotton and co-workers (see Cotton, F. A.; Dori, Z.; Marler, D. O.; Schwotzer, W. Inorg. Chem. 1984, 23, 4033-8). Recently Sasaki and Richens have independently studied the kinetics of terminal water exchange in [M.sub.3 (.mu..sub.3 -O).sub.2 (O.sub.2 CCH.sub.3).sub.6 (H.sub.2 O).sub.3 ].sup.2+ (M=Mo, W) (Nakata, K.; Nagasawa, A.; Soyama, N.; Sasaki, Y.; Ito, T. Inorg. Chem. 1991, 30, 1575-9. Powell, G.; Richens. D. T. Inorg. Chem. 1993, 32, 4021). Their results show that the water exchange rate in this system is several orders of magnitude slower than in "M.sub.3 (IV) aquo ion", [M.sub.3 (.mu..sub.3 -O)(.mu.-O).sub.3 (H.sub.2 O).sub.9 ].sup.4+ (M=Mo, W), and that the degree of inertness is more profound in tungsten case.
Although exchange of the bridging carboxylates has been performed on reactive molybdenum di- and tri-nuclear systems (Telser, J.; Drago, R. S. Inorg. Chem. 1984, 23, 1978; Nakata, K.; Yamaguchi, T.; Sasak, Y.; Ito, T. Chem. Lett. 1992. 6, 983-6), no such direct carboxylate exchange has been successfully performed on the bi-oxo capped W.sub.3 system, [W.sub.3 (.mu..sub.3 -O).sub.2 (O.sub.2 CR).sub.6 L.sub.3 ].sup.n.+-..